So, I'm thinking of trying to combine positional data from the subset of Hipparcos you have on your stellar mapping page with spectral and luminosity data from other sources such as Yale, Gliese, and the ISDB. What do you suggest in the way of determining which Hipparcos entry is which Yale, Gliese, or ISDB entry?

So, I'm thinking of trying to combine positional data from the subset of Hipparcos you have on your stellar mapping page with spectral and luminosity data from other sources such as Yale, Gliese, and the ISDB. What do you suggest in the way of determining which Hipparcos entry is which Yale, Gliese, or ISDB entry?

I'm still going over the new data - annoyingly the 7.7ly link I had found using a brown dwarf (see here) between the RECONS data and the Arcturus/Eta Bootis 'clump' has disappeared when I used the XHIP data instead of New Reduction. Humph.

Let's take a look at HIP 72944 (a.k.a CE Bootis, a binary M V system) - this is the system that the brown dwarf linked to in NRH but not in XHIP that I mentioned above. The parallax for it in each version of Hipparcos is:

I'm honestly not sure which is better for parallaxes out of the original HIP (HIP1) or New Reduction HIP (NRH). XHIP "elected" to use HIP1 parallaxes over NRH parallaxes for the multiple systems if the parallax error in NRH is higher than the parallax error in HIP1, but from the sound of it they're just assuming that the HIP1 parallax in these cases is more accurate. In this case (at least) they seem to have just used the HIP1 parallax and tacked on the NRH error bar.

The other complication is that it turns out that the BD that is connecting to CE Bootis actually had its parallax determined "spectrophotometrically", which isn't as accurate as trigonometric parallax (it's not even parallax at all - it's "find it's magnitude, figure out what its spectral type is and what luminosity it should have, and then figure out the distance from that). So it could actually be close enough to CE Bootis to link to it (whether I use CE Bootis' flexible error bars or not). Or it might not be, for all I know. Sigh.

EDIT: On further examination, the BD in question has a "spectrophotometric parallax" of 127 mas ± 27 mas. Which is a ridonkulous error bar that essentially means "I can put the damn thing anywhere I like in that area", so... ノಠ益ಠ)ノ彡┻━┻

I think there comes a point where one has to draw a line, or one will get tied up in all these niggly little details. Short of turning every system into a line (denoting where the system could be due to its error bars) rather than a point, I think "accurate enough" will suffice. For my own purposes, I think I may just stick with the New Reduction data as it is - if I need data on the stars, I can look them up individually.

I've now replaced the New Reduction Hipparcos data with the brand new Extended Hipparcos dataset, so if you downloaded that previously then please head back and download the new data! Also, my stellar mapping site now proudly bears the Atomic Rockets Seal of Approval!

I’ve added a new Brown Dwarf dataset to the Stellar Mapping page! This should hopefully be the last major update to the stellar datasets for a while – the next project on the list is to figure out what the reworked Arms for 2300AD might look like based on the realistic data.

I've also made some major updates to the other datasets on the Stellar Mapping page, so if you're using them then you'll want to download the new versions!

Using the 2300AD rules, I would like to rethink the world map and the Arms.

Even if the "arms" are interconnected, I still think Arms would develop as countries that are allies work together and countries that are "enemies" will avoid developing worlds that require support, or passing through, enemy outposts.

Can you imagine the modern US developing a system that requires a stop over at an outpost controlled by North Korea? Wouldn't happen, so the Arms will likely still develop, at least at the beginning, but sort of blend together as colonies started founding their own secondary colonies. Eventually (long after the 2300 time) things will look much more random.

On your stellar mapping page, you indicate that you corrected some errors and combined some multiple stars from the HIPX catalog. How did you do that? I am interested in data out to about 1000 pc, so starting from your 300 LY database doesn't get me too far. How did you determine these errors:

While most of the HIPX parallax data is taken from the New Reduction, some of the multiple star system parallaxes were revealed to be inaccurate – in these cases, the star system’s parallax was replaced by data from the Original Hipparcos dataset.

On your stellar mapping page, you indicate that you corrected some errors and combined some multiple stars from the HIPX catalog. How did you do that? I am interested in data out to about 1000 pc, so starting from your 300 LY database doesn't get me too far. How did you determine these errors:

[i]While most of the HIPX parallax data is taken from the New Reduction, some of the multiple star system parallaxes were revealed to be inaccurate – in these cases, the star system’s parallax was replaced by data from the Original Hipparcos dataset.

For the first part (the fixing of the multiple star parallaxes), the authors of the Extended Hipparcos paper did that, not me. You'd have to read the HipX paper that I link to there to understand what they did - I think they basically run some kind of routine that somehow compares the observed parallaxes to the values that are expected for something at that distance, or something like that.

Quote:

And how did you combine the multiples?

You can make Multiple systems in Astrosynthesis where all the stars have the same ID number (and I edited the XYZ coords so that they are the same for each component - I explain what I did on the page:

Quote:

Separated multiple-star systems in HIPX have now been re-combined as single systems. If the A/B/C components of multiple-star systems were separated by several lightyears in the original data (due to parallax inconsistencies) then they have now been combined as Multiple systems at the location of the A star (this is assumed to be at the correct distance for the system). Some stars were originally listed as solitary “A” components without any corresponding B components listed at all – these have been left as single stars, but it can be assumed that they are actually multiple stars with the other components at the same location as the A star.

I am still (slowly) working on this, BTW. Next up is an updated Brown Dwarf list with the new near-sol data from WISE, and then I also plan to combine the databases into a single file to make it easier to download them. I don't have a timeline for those, but they'll be up "soon".

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